<!DOCTYPE html><html class=split lang=en-US-x-hixie><script src=../link-fixup.js defer=""></script>
<!-- Mirrored from html.spec.whatwg.org/multipage/iana.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 10 Sep 2025 08:35:57 GMT -->
<!-- Added by HTTrack --><meta http-equiv="content-type" content="text/html;charset=utf-8" /><!-- /Added by HTTrack -->
<meta charset=utf-8><meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name=viewport><title>HTML Standard</title><meta content=#3c790a name=theme-color><meta content="light dark" name=color-scheme><link rel=stylesheet href=../../resources.whatwg.org/standard-shared-with-dev.css crossorigin=""><link rel=stylesheet href=../../resources.whatwg.org/standard.css crossorigin=""><link rel=stylesheet href=../../resources.whatwg.org/spec.css crossorigin=""><link rel=icon href=https://resources.whatwg.org/logo.svg crossorigin=""><link rel=stylesheet href=../styles.css crossorigin=""><script>
   function toggleStatus(div) {
     div.parentNode.classList.toggle('wrapped');
   }
   function setLinkFragment(link) {
     link.hash = location.hash;
   }
  </script><body>
  
  <script defer="" crossorigin="" src=../html-dfn.js></script>
  
  <header id=head class="head with-buttons">
   <a href=https://whatwg.org/ class=logo><img width=100 alt=WHATWG crossorigin="" class=darkmode-aware src=https://resources.whatwg.org/logo.svg height=100></a>
   <hgroup><h1 class=allcaps>HTML</h1><p id=living-standard>Living Standard — Last Updated <span class=pubdate>10 September 2025</span></hgroup>
   
   

   
  </header>

  

  

  

  
  

  
  

  

  <nav><a href=obsolete.html>← 16 Obsolete features</a> — <a href=index.html>Table of Contents</a> — <a href=indices.html>Index →</a></nav><ol class=toc><li id=toc-iana><a href=iana.html#iana><span class=secno>17</span> IANA considerations</a><ol><li><a href=iana.html#text/html><span class=secno>17.1</span> <code>text/html</code></a><li><a href=iana.html#multipart/x-mixed-replace><span class=secno>17.2</span> <code>multipart/x-mixed-replace</code></a><li><a href=iana.html#application/xhtml+xml><span class=secno>17.3</span> <code>application/xhtml+xml</code></a><li><a href=iana.html#text/ping><span class=secno>17.4</span> <code>text/ping</code></a><li><a href=iana.html#application/microdata+json><span class=secno>17.5</span> <code>application/microdata+json</code></a><li><a href=iana.html#application/speculationrules+json><span class=secno>17.6</span> <code>application/speculationrules+json</code></a><li><a href=iana.html#text/event-stream><span class=secno>17.7</span> <code>text/event-stream</code></a><li><a href=iana.html#web+-scheme-prefix><span class=secno>17.8</span> <code>web+</code> scheme prefix</a></ol></ol><h2 id=iana><span class=secno>17</span> IANA considerations<a href=#iana class=self-link></a></h2>

  


  <h3 id=text/html><span class=secno>17.1</span> <dfn><code>text/html</code></dfn><a href=#text/html class=self-link></a></h3>

  <p>This registration is for community review and will be submitted to the IESG for review,
  approval, and registration with IANA.</p>

  

  

  <dl><dt>Type name:<dd>text<dt>Subtype name:<dd>html<dt>Required parameters:<dd>No required parameters<dt>Optional parameters:<dd>
    <dl><dt><code>charset</code><dd>
      <p>The <code>charset</code> parameter may be provided to specify the
      <a id="text/html:document's-character-encoding" href=https://dom.spec.whatwg.org/#concept-document-encoding data-x-internal="document's-character-encoding">document's character encoding</a>, overriding any <a href=semantics.html#character-encoding-declaration id=text/html:character-encoding-declaration>character encoding declarations</a> in the document other than a Byte Order
      Mark (BOM). The parameter's value must be an <a id=text/html:ascii-case-insensitive href=https://infra.spec.whatwg.org/#ascii-case-insensitive data-x-internal=ascii-case-insensitive>ASCII case-insensitive</a> match for the
      string "<code>utf-8</code>". <a href=references.html#refsENCODING>[ENCODING]</a></p>
     </dl>
   <dt>Encoding considerations:<dd>
    8bit (see the section on <a href=semantics.html#character-encoding-declaration id=text/html:character-encoding-declaration-2>character encoding
    declarations</a>)
   <dt>Security considerations:<dd>
    <p>Entire novels have been written about the security considerations that apply to HTML
    documents. Many are listed in this document, to which the reader is referred for more details.
    Some general concerns bear mentioning here, however:</p>

    <p>HTML is scripted language, and has a large number of APIs (some of which are described in
    this document). Script can expose the user to potential risks of information leakage, credential
    leakage, cross-site scripting attacks, cross-site request forgeries, and a host of other
    problems. While the designs in this specification are intended to be safe if implemented
    correctly, a full implementation is a massive undertaking and, as with any software, user agents
    are likely to have security bugs.</p>

    <p>Even without scripting, there are specific features in HTML which, for historical reasons,
    are required for broad compatibility with legacy content but that expose the user to unfortunate
    security problems. In particular, the <code id=text/html:the-img-element><a href=embedded-content.html#the-img-element>img</a></code> element can be used in conjunction with
    some other features as a way to effect a port scan from the user's location on the Internet.
    This can expose local network topologies that the attacker would otherwise not be able to
    determine.</p>

    <p>HTML relies on a compartmentalization scheme sometimes known as the <i>same-origin
    policy</i>. An <a id=text/html:concept-origin href=browsers.html#concept-origin>origin</a> in most cases consists of all the pages served from the same
    host, on the same port, using the same protocol.</p>

    <p>It is critical, therefore, to ensure that any untrusted content that forms part of a site be
    hosted on a different <a id=text/html:concept-origin-2 href=browsers.html#concept-origin>origin</a> than any sensitive content on that site. Untrusted
    content can easily spoof any other page on the same origin, read data from that origin, cause
    scripts in that origin to execute, submit forms to and from that origin even if they are
    protected from cross-site request forgery attacks by unique tokens, and make use of any
    third-party resources exposed to or rights granted to that origin.</p>
   <dt>Interoperability considerations:<dd>
    Rules for processing both conforming and non-conforming content
    are defined in this specification.
   <dt>Published specification:<dd id=authors-using-html>
    This document is the relevant specification. Labeling a resource
    with the <code id=text/html:text/html><a href=#text/html>text/html</a></code> type asserts that the resource is
    an <a href=https://dom.spec.whatwg.org/#html-document id=text/html:html-documents data-x-internal=html-documents>HTML document</a> using
    <a id=text/html:syntax href=syntax.html#syntax>the HTML syntax</a>.
   <dt>Applications that use this media type:<dd>
    Web browsers, tools for processing web content, HTML authoring
    tools, search engines, validators.
   <dt>Additional information:<dd>
    <dl><dt>Magic number(s):<dd>No sequence of bytes can uniquely identify an HTML
     document. More information on detecting HTML documents is
     available in <cite>MIME Sniffing</cite>. <a href=references.html#refsMIMESNIFF>[MIMESNIFF]</a><dt>File extension(s):<dd>"<code>html</code>" and "<code>htm</code>"
     are commonly, but certainly not exclusively, used as the
     extension for HTML documents.<dt>Macintosh file type code(s):<dd><code>TEXT</code></dl>
   <dt>Person &amp; email address to contact for further information:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Intended usage:<dd>Common<dt>Restrictions on usage:<dd>No restrictions apply.<dt>Author:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Change controller:<dd>W3C</dl>

  <p><a href=https://url.spec.whatwg.org/#concept-url-fragment id=text/html:concept-url-fragment data-x-internal=concept-url-fragment>Fragments</a> used with <code id=text/html:text/html-2><a href=#text/html>text/html</a></code> resources
  either refer to the <a id=text/html:the-indicated-part-of-the-document href=browsing-the-web.html#the-indicated-part-of-the-document>indicated part</a> of the corresponding <code id=text/html:document><a href=dom.html#document>Document</a></code>, or
  provide state information for in-page scripts.</p>



  <h3 id=multipart/x-mixed-replace><span class=secno>17.2</span> <dfn><code>multipart/x-mixed-replace</code></dfn><a href=#multipart/x-mixed-replace class=self-link></a></h3>

  <p>This registration is for community review and will be submitted to the IESG for review,
  approval, and registration with IANA.</p>

  

  <dl><dt>Type name:<dd>multipart<dt>Subtype name:<dd>x-mixed-replace<dt>Required parameters:<dd>
    <ul class=brief><li><code>boundary</code> (defined in RFC2046) <a href=references.html#refsRFC2046>[RFC2046]</a>
    </ul>
   <dt>Optional parameters:<dd>No optional parameters.<dt>Encoding considerations:<dd>binary<dt>Security considerations:<dd>
    Subresources of a <code id=multipart/x-mixed-replace:multipart/x-mixed-replace><a href=#multipart/x-mixed-replace>multipart/x-mixed-replace</a></code>
    resource can be of any type, including types with non-trivial
    security implications such as <code id=multipart/x-mixed-replace:text/html><a href=#text/html>text/html</a></code>.
   <dt>Interoperability considerations:<dd>
    None.
   <dt>Published specification:<dd>
    This specification describes processing rules for web browsers.
    Conformance requirements for generating resources with this type are the same as for <code id=multipart/x-mixed-replace:multipart/mixed><a href=indices.html#multipart/mixed>multipart/mixed</a></code>. <a href=references.html#refsRFC2046>[RFC2046]</a>
   <dt>Applications that use this media type:<dd>
    This type is intended to be used in resources generated by web servers, for consumption by web browsers.
   <dt>Additional information:<dd>
    <dl><dt>Magic number(s):<dd>No sequence of bytes can uniquely identify a <code id=multipart/x-mixed-replace:multipart/x-mixed-replace-2><a href=#multipart/x-mixed-replace>multipart/x-mixed-replace</a></code> resource.<dt>File extension(s):<dd>No specific file extensions are recommended for this type.<dt>Macintosh file type code(s):<dd>No specific Macintosh file type codes are recommended for this type.</dl>
   <dt>Person &amp; email address to contact for further information:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Intended usage:<dd>Common<dt>Restrictions on usage:<dd>No restrictions apply.<dt>Author:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Change controller:<dd>W3C</dl>

  <p><a href=https://url.spec.whatwg.org/#concept-url-fragment id=multipart/x-mixed-replace:concept-url-fragment data-x-internal=concept-url-fragment>Fragments</a> used with
  <code id=multipart/x-mixed-replace:multipart/x-mixed-replace-3><a href=#multipart/x-mixed-replace>multipart/x-mixed-replace</a></code> resources apply to each body part as defined by the type
  used by that body part.</p>


  <h3 id=application/xhtml+xml><span class=secno>17.3</span> <dfn><code>application/xhtml+xml</code></dfn><a href=#application/xhtml+xml class=self-link></a></h3>

  <p>This registration is for community review and will be submitted to the IESG for review,
  approval, and registration with IANA.</p>

  

  

  <dl><dt>Type name:<dd>application<dt>Subtype name:<dd>xhtml+xml<dt>Required parameters:<dd>Same as for <code id=application/xhtml+xml:application/xml><a href=indices.html#application/xml>application/xml</a></code> <a href=references.html#refsRFC7303>[RFC7303]</a><dt>Optional parameters:<dd>Same as for <code id=application/xhtml+xml:application/xml-2><a href=indices.html#application/xml>application/xml</a></code> <a href=references.html#refsRFC7303>[RFC7303]</a><dt>Encoding considerations:<dd>Same as for <code id=application/xhtml+xml:application/xml-3><a href=indices.html#application/xml>application/xml</a></code> <a href=references.html#refsRFC7303>[RFC7303]</a><dt>Security considerations:<dd>Same as for <code id=application/xhtml+xml:application/xml-4><a href=indices.html#application/xml>application/xml</a></code> <a href=references.html#refsRFC7303>[RFC7303]</a><dt>Interoperability considerations:<dd>Same as for <code id=application/xhtml+xml:application/xml-5><a href=indices.html#application/xml>application/xml</a></code> <a href=references.html#refsRFC7303>[RFC7303]</a><dt id=authors-using-xhtml>Published specification:<dd>Labeling a resource with the <code id=application/xhtml+xml:application/xhtml+xml><a href=#application/xhtml+xml>application/xhtml+xml</a></code> type asserts that the
   resource is an XML document that likely has a <a id=application/xhtml+xml:document-element href=https://dom.spec.whatwg.org/#document-element data-x-internal=document-element>document element</a> from the <a id=application/xhtml+xml:html-namespace-2 href=https://infra.spec.whatwg.org/#html-namespace data-x-internal=html-namespace-2>HTML
   namespace</a>. Thus, the relevant specifications are <cite>XML</cite>, <cite>Namespaces in
   XML</cite>, and this specification. <a href=references.html#refsXML>[XML]</a> <a href=references.html#refsXMLNS>[XMLNS]</a><dt>Applications that use this media type:<dd>Same as for <code id=application/xhtml+xml:application/xml-6><a href=indices.html#application/xml>application/xml</a></code> <a href=references.html#refsRFC7303>[RFC7303]</a><dt>Additional information:<dd>
    <dl><dt>Magic number(s):<dd>Same as for <code id=application/xhtml+xml:application/xml-7><a href=indices.html#application/xml>application/xml</a></code> <a href=references.html#refsRFC7303>[RFC7303]</a><dt>File extension(s):<dd>"<code>xhtml</code>" and "<code>xht</code>" are sometimes used as
     extensions for XML resources that have a <a id=application/xhtml+xml:document-element-2 href=https://dom.spec.whatwg.org/#document-element data-x-internal=document-element>document element</a> from the <a id=application/xhtml+xml:html-namespace-2-2 href=https://infra.spec.whatwg.org/#html-namespace data-x-internal=html-namespace-2>HTML
     namespace</a>.<dt>Macintosh file type code(s):<dd><code>TEXT</code></dl>
   <dt>Person &amp; email address to contact for further information:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Intended usage:<dd>Common<dt>Restrictions on usage:<dd>No restrictions apply.<dt>Author:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Change controller:<dd>W3C</dl>

  <p><a href=https://url.spec.whatwg.org/#concept-url-fragment id=application/xhtml+xml:concept-url-fragment data-x-internal=concept-url-fragment>Fragments</a> used with
  <code id=application/xhtml+xml:application/xhtml+xml-2><a href=#application/xhtml+xml>application/xhtml+xml</a></code> resources have the same semantics as with any
  <a id=application/xhtml+xml:xml-mime-type href=https://mimesniff.spec.whatwg.org/#xml-mime-type data-x-internal=xml-mime-type>XML MIME type</a>. <a href=references.html#refsRFC7303>[RFC7303]</a></p>


  <h3 id=text/ping><span class=secno>17.4</span> <dfn><code>text/ping</code></dfn><a href=#text/ping class=self-link></a></h3>

  <p>This registration is for community review and will be submitted to the IESG for review,
  approval, and registration with IANA.</p>

  

  <dl><dt>Type name:<dd>text<dt>Subtype name:<dd>ping<dt>Required parameters:<dd>No parameters<dt>Optional parameters:<dd>
    <dl><dt><code>charset</code><dd>
      <p>The <code>charset</code> parameter may be provided. The parameter's value must be
      "<code>utf-8</code>". This parameter serves no purpose; it is only allowed for
      compatibility with legacy servers.</p>
     </dl>
   <dt>Encoding considerations:<dd>Not applicable.<dt>Security considerations:<dd>
    <p>If used exclusively in the fashion described in the context of
    <a id=text/ping:hyperlink-auditing href=links.html#hyperlink-auditing>hyperlink auditing</a>, this type introduces no new
    security concerns.</p>
   <dt>Interoperability considerations:<dd>
    Rules applicable to this type are defined in this specification.
   <dt>Published specification:<dd>
    This document is the relevant specification.
   <dt>Applications that use this media type:<dd>
    Web browsers.
   <dt>Additional information:<dd>
    <dl><dt>Magic number(s):<dd><code id=text/ping:text/ping><a href=#text/ping>text/ping</a></code> resources always consist of the four
     bytes 0x50 0x49 0x4E 0x47 (`<code>PING</code>`).<dt>File extension(s):<dd>No specific file extension is recommended for this type.<dt>Macintosh file type code(s):<dd>No specific Macintosh file type codes are recommended for this type.</dl>
   <dt>Person &amp; email address to contact for further information:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Intended usage:<dd>Common<dt>Restrictions on usage:<dd>Only intended for use with HTTP POST requests generated as part
   of a web browser's processing of the <code id=text/ping:ping><a href=links.html#ping>ping</a></code> attribute.<dt>Author:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Change controller:<dd>W3C</dl>

  <p><a href=https://url.spec.whatwg.org/#concept-url-fragment id=text/ping:concept-url-fragment data-x-internal=concept-url-fragment>Fragments</a> have no meaning with
  <code id=text/ping:text/ping-2><a href=#text/ping>text/ping</a></code> resources.</p>


  <h3 id=application/microdata+json><span class=secno>17.5</span> <dfn><code>application/microdata+json</code></dfn><a href=#application/microdata+json class=self-link></a></h3>

  <p>This registration is for community review and will be submitted to the IESG for review,
  approval, and registration with IANA.</p>

  

  <dl><dt>Type name:<dd>application<dt>Subtype name:<dd>microdata+json<dt>Required parameters:<dd>Same as for <code id=application/microdata+json:application/json><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Optional parameters:<dd>Same as for <code id=application/microdata+json:application/json-2><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Encoding considerations:<dd>8bit (always UTF-8)<dt>Security considerations:<dd>Same as for <code id=application/microdata+json:application/json-3><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Interoperability considerations:<dd>Same as for <code id=application/microdata+json:application/json-4><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Published specification:<dd>
    Labeling a resource with the <code id=application/microdata+json:application/microdata+json><a href=#application/microdata+json>application/microdata+json</a></code> type asserts that the
    resource is a JSON text that consists of an object with a single entry called "<code>items</code>" consisting of an array of entries, each of which consists of an object
    with an entry called "<code>id</code>" whose value is a string, an entry called "<code>type</code>" whose value is another string, and an entry called "<code>properties</code>" whose value is an object whose entries each have a value consisting
    of an array of either objects or strings, the objects being of the same form as the objects in
    the aforementioned "<code>items</code>" entry. Thus, the relevant specifications are
    <cite>JSON</cite> and this specification. <a href=references.html#refsJSON>[JSON]</a>
   <dt>Applications that use this media type:<dd>
    <p>Applications that transfer data intended for use with HTML's microdata feature, especially in
    the context of drag-and-drop, are the primary application class for this type.</p>
   <dt>Additional information:<dd>
    <dl><dt>Magic number(s):<dd>Same as for <code id=application/microdata+json:application/json-5><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>File extension(s):<dd>Same as for <code id=application/microdata+json:application/json-6><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Macintosh file type code(s):<dd>Same as for <code id=application/microdata+json:application/json-7><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a></dl>
   <dt>Person &amp; email address to contact for further information:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Intended usage:<dd>Common<dt>Restrictions on usage:<dd>No restrictions apply.<dt>Author:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Change controller:<dd>W3C</dl>

  <p><a href=https://url.spec.whatwg.org/#concept-url-fragment id=application/microdata+json:concept-url-fragment data-x-internal=concept-url-fragment>Fragments</a> used with
  <code id=application/microdata+json:application/microdata+json-2><a href=#application/microdata+json>application/microdata+json</a></code> resources have the same semantics as when used with
  <code id=application/microdata+json:application/json-8><a href=indices.html#application/json>application/json</a></code> (namely, at the time of writing, no semantics at all).
  <a href=references.html#refsJSON>[JSON]</a></p>

  <h3 id=application/speculationrules+json><span class=secno>17.6</span> <dfn><code>application/speculationrules+json</code></dfn><a href=#application/speculationrules+json class=self-link></a></h3>

  <p>This registration is for community review and will be submitted to the IESG for review,
  approval, and registration with IANA.</p>

  

  <dl><dt>Type name:<dd>application<dt>Subtype name:<dd>microdata+json<dt>Required parameters:<dd>Same as for <code id=application/speculationrules+json:application/json><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Optional parameters:<dd>Same as for <code id=application/speculationrules+json:application/json-2><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Encoding considerations:<dd>8bit (always UTF-8)<dt>Security considerations:<dd>Same as for <code id=application/speculationrules+json:application/json-3><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Interoperability considerations:<dd>Same as for <code id=application/speculationrules+json:application/json-4><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Published specification:<dd>
    Labeling a resource with the <code id=application/speculationrules+json:application/microdata+json><a href=#application/microdata+json>application/microdata+json</a></code> type asserts that the
    resource is a JSON text that follows the <a id=application/speculationrules+json:speculation-rule-set-authoring-requirements href=speculative-loading.html#speculation-rule-set-authoring-requirements>speculation rule set authoring requirements</a>. Thus, the relevant specifications are
    <cite>JSON</cite> and this specification. <a href=references.html#refsJSON>[JSON]</a>
   <dt>Applications that use this media type:<dd>
    <p>Web browsers.</p>
   <dt>Additional information:<dd>
    <dl><dt>Magic number(s):<dd>Same as for <code id=application/speculationrules+json:application/json-5><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>File extension(s):<dd>Same as for <code id=application/speculationrules+json:application/json-6><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a><dt>Macintosh file type code(s):<dd>Same as for <code id=application/speculationrules+json:application/json-7><a href=indices.html#application/json>application/json</a></code> <a href=references.html#refsJSON>[JSON]</a></dl>
   <dt>Person &amp; email address to contact for further information:<dd>Domenic Denicola &lt;d@domenic.me><dt>Intended usage:<dd>Common<dt>Restrictions on usage:<dd>No restrictions apply.<dt>Author:<dd>Domenic Denicola &lt;d@domenic.me><dt>Change controller:<dd>WHATWG</dl>

  <p><a href=https://url.spec.whatwg.org/#concept-url-fragment id=application/speculationrules+json:concept-url-fragment data-x-internal=concept-url-fragment>Fragments</a> used with
  <code id=application/speculationrules+json:application/speculationrules+json><a href=#application/speculationrules+json>application/speculationrules+json</a></code> resources have the same semantics as when used with
  <code id=application/speculationrules+json:application/json-8><a href=indices.html#application/json>application/json</a></code> (namely, at the time of writing, no semantics at all).
  <a href=references.html#refsJSON>[JSON]</a></p>


  <h3 id=text/event-stream><span class=secno>17.7</span> <dfn><code>text/event-stream</code></dfn><a href=#text/event-stream class=self-link></a></h3>

  <p>This registration is for community review and will be submitted to the IESG for review,
  approval, and registration with IANA.</p>

  

  <dl><dt>Type name:<dd>text<dt>Subtype name:<dd>event-stream<dt>Required parameters:<dd>No parameters<dt>Optional parameters:<dd>
    <dl><dt><code>charset</code><dd>
      <p>The <code>charset</code> parameter may be provided. The parameter's value must be
      "<code>utf-8</code>". This parameter serves no purpose; it is only allowed for
      compatibility with legacy servers.</p>
     </dl>
   <dt>Encoding considerations:<dd>8bit (always UTF-8)<dt>Security considerations:<dd>
    <p>An event stream from an origin distinct from the origin of the content consuming the event
    stream can result in information leakage. To avoid this, user agents are required to apply CORS
    semantics. <a href=references.html#refsFETCH>[FETCH]</a></p>

    <p>Event streams can overwhelm a user agent; a user agent is expected to apply suitable
    restrictions to avoid depleting local resources because of an overabundance of information from
    an event stream.</p>

    <p>Servers can be overwhelmed if a situation develops in which the server is causing clients to
    reconnect rapidly. Servers should use a 5xx status code to indicate capacity problems, as this
    will prevent conforming clients from reconnecting automatically.</p>
   <dt>Interoperability considerations:<dd>
    Rules for processing both conforming and non-conforming content are defined in this
    specification.
   <dt>Published specification:<dd>
    This document is the relevant specification.
   <dt>Applications that use this media type:<dd>
    Web browsers and tools using web services.
   <dt>Additional information:<dd>
    <dl><dt>Magic number(s):<dd>No sequence of bytes can uniquely identify an event stream.<dt>File extension(s):<dd>No specific file extensions are recommended for this type.<dt>Macintosh file type code(s):<dd>No specific Macintosh file type codes are recommended for this type.</dl>
   <dt>Person &amp; email address to contact for further information:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Intended usage:<dd>Common<dt>Restrictions on usage:<dd>This format is only expected to be used by dynamic open-ended streams served using HTTP or a
   similar protocol. Finite resources are not expected to be labeled with this type.<dt>Author:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Change controller:<dd>W3C</dl>

  <p><a href=https://url.spec.whatwg.org/#concept-url-fragment id=text/event-stream:concept-url-fragment data-x-internal=concept-url-fragment>Fragments</a> have no meaning with
  <code id=text/event-stream:text/event-stream><a href=#text/event-stream>text/event-stream</a></code> resources.</p>


  <h3 id=web+-scheme-prefix><span class=secno>17.8</span> <dfn><code>web+</code> scheme prefix</dfn><a href=#web+-scheme-prefix class=self-link></a></h3>

  <p>This section describes a convention for use with the IANA URI scheme registry. It does not
  itself register a specific scheme. <a href=references.html#refsRFC7595>[RFC7595]</a></p>

  <dl><dt>Scheme name:<dd>
    Schemes starting with the four characters "<code>web+</code>" followed by one or more letters in the range
    <code>a</code>-<code>z</code>.
   <dt>Status:<dd>Permanent<dt>Scheme syntax:<dd>Scheme-specific.<dt>Scheme semantics:<dd>Scheme-specific.<dt>Encoding considerations:<dd>All "<code>web+</code>" schemes should use UTF-8 encodings where relevant.<dt>Applications/protocols that use this scheme name:<dd>Scheme-specific.<dt>Interoperability considerations:<dd>The scheme is expected to be used in the context of web applications.<dt>Security considerations:<dd>
    Any web page is able to register a handler for all "<code>web+</code>" schemes. As
    such, these schemes must not be used for features intended to be core platform features (e.g.,
    HTTP). Similarly, such schemes must not store confidential information in their URLs, such as
    usernames, passwords, personal information, or confidential project names.
   <dt>Contact:<dd>Ian Hickson &lt;ian@hixie.ch><dt>Change controller:<dd>Ian Hickson &lt;ian@hixie.ch><dt>References:<dd>
    <cite>Custom scheme handlers</cite>, HTML Living Standard:
    <a href=system-state.html#custom-handlers>https://html.spec.whatwg.org/#custom-handlers</a>
   </dl>

  



  <nav><a href=obsolete.html>← 16 Obsolete features</a> — <a href=index.html>Table of Contents</a> — <a href=indices.html>Index →</a></nav>
